A large static magnetic field is used by Magnetic Resonance Imaging (MRI) scanners to align the nuclear spins of atoms as part of the procedure for producing images within the body of a patient. This large static magnetic field is referred to as the B0 field. During an MRI scan, Radio Frequency (RF) pulses generated by one or more transmitter coils cause perturbations to the local magnetic field, and RF signals emitted by the nuclear spins are detected by one or more receiver coils. These RF signals are used to construct the MR images. These coils can also be referred to as antennas. Further, the transmitter and receiver coils can also be integrated into one or more transceiver coils that perform both functions. It is understood that the use of the term transceiver coil also refers to systems where separate transmitter and receiver coils are used. The transmitted RF field is referred to as the B1 field.
MRI scanners are able to construct images of either slices or volumes. A slice is a thin volume that is only one voxel thick. A voxel is a small volume over which the MR signal is averaged, and represents the resolution of the MR image. A voxel may also be referred to as a pixel herein.
Dixon methods of magnetic resonance imaging include a family of techniques for producing separate water and lipid (fat) images. The various Dixon techniques such as, but not limited to, two-point Dixon methods, three-point Dixon methods, and multi-point Dixon methods are collectively referred to herein as Dixon techniques or methods. The terminology to describe the Dixon techniques is well known and has been the subject of many review articles and is present in standard texts on Magnetic Resonance Imaging. For example, the “Handbook of MRI Pulse Sequences” by Bernstein et al., published by Elsevier Academic Press in 2004, contains a review of some Dixon techniques on pages 857 to 887.
United States patent application US 20140184219 A1 discloses calculating a zero phase estimation of a B1 phase map using a B0 inhomogeneity map.